Dirac Surface States in Intrinsic Magnetic Topological Insulators EuSn2As2 and

Abstract

In magnetic topological insulators (TIs), the interplay between magnetic order and nontrivial topology can induce fascinating topological quantum phenomena, such as the quantum anomalous Hall effect, chiral Majorana fermions and axion electrodynamics. Recently, a great deal of attention has been focused on the intrinsic magnetic TIs, where disorder effects can be eliminated to a large extent, which is expected to facilitate the emergence of topological quantum phenomena. In despite of intensive efforts, the experimental evidence of topological surface states (SSs) remains elusive. Here, by combining first-principles calculations and angle-resolved photoemission spectroscopy (ARPES) experiments, we have revealed that EnSn2As2 is an antiferromagnetic TI with observation of Dirac SSs consistent with our prediction.We also observed gapless Dirac SSs in another antiferromagnetic TI MnBi2Te4, which were missed in previous ARPES study. These results provide clear evidence for nontrivial topology of the two intrinsic magnetic TIs. Moreover, the topological SSs show no observable changes across the magnetic transitions within the experimental resolution, indicating that the magnetic order has limited effect on the topological SSs, which can be attributed to weak hybridization between the magnetic states and the topological electronic states. This provides insights for further studies that the correlations between magnetism and topological states need to be strengthened to induce larger gaps of the topological SSs, which will facilitate the realization of topological quantum phenomena at higher temperatures.

Universal gapless Dirac cone and tunable topological states in (MnBi2Te4)m(

“…This is in sharp contrast to the earlier reports of a magnetic order induced surface gap in the order of hundred-meVs in both MnBi2Te4 [2,4,9,17] and MnBi4Te7 [14,15]. On the contrary, our results are consistent with the recent observation of a gapless TSS in MnBi2Te4 [32][33][34][35]. We note that the gapless TSSs in our experiments persist to high temperatures above the magnetic transition temperatures of the materials (supplementary Fig.…”

“…1a) [9][10][11]. However, unexpected gapless topological surface states (TSSs) are observed by high-resolution ARPES measurements [32][33][34][35], raising critical questions regarding the surface magnetic structure, magnetic coupling strength and the specifics of the MnBi2Te4 material system.…”

Manipulating topological spin textures in multiferroic and polar materials

“…Both for magnetically doped topological insulators 10,11 and layered intrinsically antiferromagnetic TIs, 12 a gap in the surface states due to magnetic order was claimed in photoemission experiments. However, separate measurements casted significant doubt on these claims, [13][14][15][16] and also complimentary local probe measurements seem to indicate the absence of such a gap. [17][18][19] For surface Rashba systems similar problems are encountered for out-of-plane magnetised systems, although for in-plane magnetisation the expected shift of the bands is observed.…”

Fabrication of a novel magnetic topological heterostructure and temperature evolution of its massive Dirac cone

“…This method was further extended and complicated heterostructures composed of MnBi 2 Se 4 and Bi 2 Se 3 , or MnBi 2 Te 4 and Bi 2 Te 3 , were experimentally fabricated 11,12 . Furthermore, MnBi 2 Te 4 and MnBi 4 Te 7 called "intrinsic magnetic TIs" were realized as bulk single crystals [13][14][15][16][17][18][19][20][21][22][23] .…”

“…On the other hand, it was claimed that the DC is massless even at temperatures lower than T N [17][18][19][20][21] . The origin was described as a result of the neutralization of the net magnetic moments due to the presence of different magnetic domains within the sample 17,[19][20][21] , or the weak hybridization between the local moments and the Dirac electrons 18 . There is another work that insists that the DC was massless at 25 K, which is above T N , but no comment was made on the behavior below T N in ref.…”